With the global pandemic mostly behind us, the IEEE Transformer Committee resumed meeting again this past year with meetings in Charlotte and Milwaukee. Attendance continues to increase as the collaborative spirit to help improve the transformer guides and standards is driving participation. Here are some highlights.
INSULATING FLUIDS SUBCOMMITTEE
The working group for C57.146, IEEE Guide for Interpretation of Gasses Generated in Silicone-Immersed Transformers, has analyzed approximately 165,000 dissolved gas samples and established limits for the 90th and 95th percentile values. The task force has questions related to the data but the working group would like the guide to be similar to C57.104, Guide for the Interpretation of Gases Generated in Mineral Oil-Immersed Transformers. The benefit of analyzing the data is that IEEE will be able to establish new limits based on actual data so users will have a better understanding of the potential issues within the transformer.
The working group for C57.155, IEEE Guide for Interpretation of Gases Generated in Natural and Synthetic Ester, is formulating a DGA data collection system to collect dissolved gas data to analyze it for establishing thresholds. The working group is also considering adding normalized energy intensity (NEI), a tool that provides a weighted average based on the amount of energy it takes to create each type of fault gas. The goal is to have another diagnostic tool to determine fault severity and the actual existence of a fault.
C57.166 is the new guide for the Acceptance and Maintenance of Insulating Liquids. It is a consolidation of all fluid quality testing and will also include synthetic esters. The draft is nearly completed, with the intention to have it go to ballot by the end of the year. This guide will make it easier for users to reference a single guide for fluid quality results instead of having to reference multiple guides.
PERFORMANCE CHARACTERISTICS SUBCOMMITTEE
Within the Performance Characteristics Subcommittee, the working group for C57.149, IEEE Guide for the Application and Interpretation of Frequency Response Analysis for Oil-Immersed Transformers, finalized the guide and it has gone to ballot. The revised guide includes SFRA connection tables and case studies to help the user understand what to expect when issues such as radial displacement, axial displacement, short-circuit failures, or transportation problems occur. Once all comments have been received, the comments will be resolved before the revised guide for SFRA is published.
The working group for the IEEE Guide for Sound Level Abatement and Determination for Liquid-Immersed Power Transformers and Shunt Reactors Rated Over 500 kVA has resolved all comments from its ballot and will be published after the IEEE Standards Review Committee approves the revised document.
Within the Standards Subcommittee, the working group for C57.152, IEEE Guide for Diagnostic Field Testing of Fluid-Filled Power Transformers, Regulators, and Reactors, has updated the guide and it is ready to be voted on by the working group. If it passes, it will be submitted to the Subcommittee for approval to go to ballot. The purpose of this guide is to provide users with a document on what electrical testing should be performed throughout the life of a transformer.
The guide for Establishing Power Transformer Capability while under Geomagnetic Disturbances for the guide revision has gone to ballot. The next step will be to resolve the comments and recirculate the guide.
POWER TRANSFORMER SUBCOMMITTEE
Within the Power Transformer Subcommittee, C57.93, IEEE Guide for The Installation and Maintenance of Liquid-Filled Power Transformers, work has begun to review the existing guide. One issue noted by the task force is that the title references maintenance but the guide itself has little discussion about transformer maintenance or LTC maintenance. Maintenance presentations have been reviewed with the task force as to what relevant information should be included as part of the revised document. The task force will meet this fall to determine what — if any — maintenance will be included as part of this guide. In other areas, a separate task force has developed a cold start-up procedure for natural ester liquid-filled power transformers and has undergone testing. Because natural esters have such a high pour point, the fluid solidifies under extreme freezing conditions. Once the procedure is finalized, it is expected to be included as part of the guide.
The IEEE Guide for Application for Monitoring Equipment to Liquid-Immersed Transformers and Components has gone to ballot. This is a significant revision to the guide that includes on-line moisture and bushing monitoring. Because of the substantial updates, the working group is considering offering a tutorial within the IEEE Transformer Committee to discuss all of the changes.
An initial draft guide for the Condition Assessment of Liquid Immersed Transformers, Reactors, and Their Components was released and is currently being reviewed and updated. The objective of this new guide is to establish methodologies to monitor the transformer and all the components so corrective action can be taken to minimize damage to a component and potential failure of the transformer. Components include bushings, load tap changers, the tank, and even the insulating liquid, as the fluid is an important component of a transformer.
INSULATION LIFE SUBCOMMITTEE
Within the Insulation Life Subcommittee, a draft guide, Interpretation of Moisture Related Parameters in Liquid Immersed Transformers and Reactors was finalized and went to ballot. Currently, the comments are being resolved. This guide is for moisture in the insulation, as the insulation is a critical component. In 2006, the guide for the Acceptance and Maintenance of Insulating Mineral Oil in Electrical Equipment removed the relative saturation calculation from the document because it doesn’t accurately determine the moisture content of the paper. Many people are not aware this calculation was removed and still use this incorrect formula that extrapolates the paper saturation from the moisture content of the oil. The relative saturation of the paper can’t be determined from the water ppm of the oil. The moisture content of the transformer’s insulation is important because the combination of heat, moisture, and oxygen will accelerate the degradation of the cellulose paper.
The IEEE guide for Determination of Maximum Winding Temperature Rise in Liquid-Immersed Transformers was published and is available for purchase at IEEE.
IEEE’s standard for General Requirements and Test Procedure for Power Apparatus Bushings was published and is available for purchase at IEEE.
The IEEE standard for Design and Performance Requirements of Bushings Applied to Liquid Immersed Distribution Transformers was published and is available for purchase at IEEE.
Work continues on the guide for Application of Power Apparatus Bushings as the fifth draft has circulated for comments from the working group. These bushings are limited to those built in accordance with IEEE Std C57.19.00-1991. There is a lot of discussion regarding the overload capability of these bushings.
Scott Reed is President of MVA, a company specializing in the oil diagnostic analysis, vacuum filling, and oil processing of substation transformers throughout the United States. He received a BS in electrical engineering from North Carolina State University with a concentration in power. He performed relay system protection design work at Baltimore Gas & Electric and worked servicing transformers for 25 years before starting MVA. Scott has written and published various papers for the industry and is very active with the IEEE Transformer Committee where he serves as Chairman of the IEEE Subcommittee of Insulating Fluids; Chairman of IEEE Std. C57.93, Installation and Maintenance of Liquid Immersed Power Transformers; Vice Chairman of IEEE Std. C57.166, Acceptance and Maintenance of Insulating Liquids in Transformers; and Vice Chairman of IEEE Std. C57.637, Guide for the Reclamation of Mineral Insulating Liquids and Criteria for Its Use. He can be reached at
email@example.com or 330-498-6259.